Canon EOS RT pellicle mirror, metering ?

[jfretless]

The Canon EOS RT has a pellicle meter. According to the manual and the internets, you lose about 2/3 of a stop of light due to the mirror.

I just did a test, took my EOS RT, 35mm f2, took a meter reading of my desk with the camera's meter, iso400, f3.5, 1/20. Then my 40D, 35mm f2, same scene, camera's meter, iso400, f3.5, 1/30.

So, help me think this through... If I use a hand held meter for a incident reading, EOS RT in manual mode, do I dial in the compensation for the 2/3 stop of light loss or does the camera do it automatically?

I'm thinking I have to dial in the compensation because the camera's meter is in/near the pentaprism and is taking the meter reading of the semi transparent mirror resulting in the slower shutter speed in my test. So there's no electronic calculation going on inside the camera, when the shutter says 1/250, it's really 1/250 and not internally retarded by the camera.

Sound right?

Thanks!
John

 

[StaaleS]

The camera's built-in meter will automatically correct for the loss of light let through to the film through the fixed mirror, if you meter off-camera you must do this manually. (The camera meter does this on purpose you know, it's not accidental.)

It's about 2/3 of a stop as you say... Just compensate with the ISO setting on the meter and off you go; if you use ISO 100 film, tell the meter you are using ISO 64.

I have a 1N RS myself, it's a pleasant camera to shoot with.

 

[StaaleS]

And yes, by the way; f/11 is a true f/11 and 1/250 is a true 1/250. All the fiddling that is being done by the RT to compensate for the pellicle mirror is being done in the camera's metering, nowhere else.

 

[jfretless]

Thanks for the confirmation!

John

 

[StaaleS]

No prob; good luck with the RT!

 

[jfretless]

Actually this is my second RT. I had one prior to getting my first dSLR, the 10D. I eventually sold the first one. Then I got a 1N RS. I loved that camera, then end up selling that and got a 1V. I figured since the 1V HS did 10FPS, there were fewer reasons to keep the 1N RS. Mind you this is all the beginning of the dSLR revolution, so prices were dropping fast and furious, so I was able to get the cameras second hand at fractions of the cost of new.

I saw this RT on eBay for like $50 bucks, couldn't pass it up.

Thanks again.
John